How Arctic-alpine plants respond to global warming
500 million measurements on the impact of climate change

Date:
August 12, 2021
Source:
University of Bonn
Summary:
Researchers have studied how two characteristic Arctic-alpine plant
species respond to global warming. They did this by analyzing
almost 500 million of their own readings from the mountainous
region of Norway. The analyses show that potential consequences of
climate change are extremely dependent on the specific location of
the plants and that deciduous species in particular will benefit
from warming. The result would be a further increase in the trend
toward greening of the Arctic-alpine regions.



FULL STORY ==========================================================================
It is the most comprehensive study of its kind to date: Researchers at
the University of Bonn and the University of South-Eastern Norway have
studied how two characteristic arctic-alpine plant species respond to
global warming. They did this by analyzing almost 500 million of their
own readings from the mountainous region of Norway. The analyses show
that potential consequences of climate change are extremely dependent
on the specific location of the plants and that deciduous species in
particular will benefit from warming. The result would be a further
increase in the trend toward greening of the arctic-alpine regions. The
study is published in the journal Ecosphere.


==========================================================================
The Norwegian mountains can be pretty darn inhospitable during the colder months. Nevertheless, there are plants that cope splendidly with the
biting temperatures. They include the dwarf birch Betula nana and the
black crowberry Empetrum hermaphroditum. Both thrive in arctic-alpine conditions; this makes them typical representatives of tundra vegetation.

Up until now, it has been unclear how the growth of dwarf birch and
crowberry is influenced by specific environmental conditions. In the
alpine regions of Norway, a project has been underway for 30 years
that aims to change that. "We wired up some of the plants here and
fitted them with so-called data loggers that record the measurements,"
explains Prof. Dr. Jo"rg Lo"ffler from the Department of Geography at
the University of Bonn. A pin-like sensor records the diameter of the
trunk -- minute by minute, 365 days a year, to an accuracy of less than
a thousandth of a millimeter. At the same time, the researchers measure
solar radiation, temperature in the root zone and just above the soil
surface, and soil moisture.

Shrinkage against frost damage In the current study, researchers analyzed nearly 500 million measurements from 40 plants between 2015 and 2019. "We mainly studied how the microclimate, that is, the conditions encountered
by the individual plant, affects its growth," says Svenja Dobbert,
who is doing her doctorate in Prof. Lo"ffler's research group. This
revealed a striking rhythm in both dwarf birch and crowberry: During
the colder months, their trunk diameter shrank significantly in each
case -- a process that was reversed in the spring. However, it was not
until late summer that the deficits were made up to such an extent that
actual growth began.

"Due to low temperatures in the colder months, there is hardly any
liquid water available for the plants," Dobbert says, explaining
the finding. "They also reduce their trunk diameter by even actively
reducing the water content of their cells to avoid frost damage." Just
how important this strategy is for both species to thrive is demonstrated
by another observation: Plants that shrank very little during the winter
often showed little or no growth the following summer.

A second important finding: The deciduous dwarf birches usually grew
better after a mild winter. They therefore seem to generally benefit
from warmer winters. With the evergreen crowberries it was the other
way around. "In cold winters, there is usually less snowfall," Lo"ffler
says. "This could be an advantage for evergreen species because they
can then keep up photosynthetic activity for longer and hence enter
the growth phase earlier in the spring." It is therefore possible that
climate change is causing an increasing spread of deciduous species and
a concomitant displacement of evergreen species. Since the leaves of
deciduous plants have a comparatively large surface area (in contrast,
those of evergreen species are usually needle-like), this effect could contribute to the further greening of arctic-alpine regions.

The microclimate is crucial "However, our results also show that
microclimatic conditions can be extremely different depending on the
location," explains Lo"ffler. For instance, at exposed, windy locations,
snow cover tends to be very thin. The deciduous dwarf birch however
requires a sufficiently thick insulating layer of snow in winter.

It then has to use fewer resources to protect itself from frost. Without
this warming blanket, the dwarf birch has a difficult time. The evergreen crowberry, in contrast, benefits from the extra sunlight during such
snow-free periods.

"Overall, our measurements prove that global climate
data provide little valid evidence for local vegetation
effects," emphasizes the geographer. "Studies like ours can
potentially help us better model such complex effects and in
turn better predict the effects of climate change on plant life." ========================================================================== Story Source: Materials provided by University_of_Bonn. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Svenja Dobbert, Roland Pape, Jo"rg Lo"ffler. Contrasting growth
response
of evergreen and deciduous arctic‐alpine shrub species to
climate variability. Ecosphere, 2021; 12 (8) DOI: 10.1002/ecs2.3688 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210812145105.htm

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